The three most popular types of materials for custom sumps are Acrylic, PVC and glass.
Some say an advantage of PVC is it's an excellent insulator when compared to acrylic and glass (Acrylic being better than glass in this regard). The downside to PVC is it is absolutely not a material for beginners and does require some particular knowledge and specific tools to work with. It is also not quite as versatile as Acrylic either when it comes to customization.
Glass is easiest to clean and as mentioned above someone with very little experience and relatively cheap tools can easily modify or add things to them. If your looking for a Refugium in a glass sump it's a little more difficult to add one without a lot of light spillage. There are ways but they aren't super easy to do or cheap depending on which route you go. You can build these sumps yourself though with relative ease and they tend to be rather budget friendly as you can find cheap tanks online and buy or make the baffles on your own. You can also go the expensive route and have a custom glass sump built for you. Virtually any custom aquarium manufacturer will build sumps as well, these can be a little expensive but nowhere near the cost of acrylic or PVC custom sumps.
And Acrylic, the go to material for most manufacturers. Not always the easiest to clean but an incredibly flexible material. Found in all colors one could possibly want and customizable to almost no end. With some playing around most can work with acrylic like they can with glass, it does require some rather expensive tools to get into some of the fancier things that can be done with it though. These sumps can get crazy expensive depending on what you would like to do with them but that's really up to the purchaser in the end as there are relatively cheap mass produced options on the market right now.
As for overall, I think they are all great options and it comes down to what you want out of a sump. If you want something that just works, a cheap used tank with glass or acrylic baffles DIY installed will work just fine. If you want fancy colors, doohickies and sport car lighting, go with custom acrylic. There are many in between options as well.